Polling architectures, as pervasive as they are today, did not come about due to their efficiency. Whether you are maintaining a popular endpoint (Twitter), or trying to get near real-time news (RSS), neither side benefits from this architecture. Over the years we've built a number of crutches in the form of Cache headers, ETags, accelerators, but none have fundamentally solved the problem - because the client remains 'dumb' the burden is still always on the server. For that reason, it's worth paying attention to some of the technologies which are seeking to reverse this trend: ReverseHTTP & WebSockets.